1. Field of the Invention
This invention relates to the preparation of an isoxazole. More particularly this invention relates to a method of optimizing the yield of 3-amino-5-(t-butyl)isoxazole over the yield of the isomeric 5-amino-3-(t-butyl)isoxazole. The 3-amino-5-(t-butyl)isoxazole is useful as an intermediate in the preparation of isoxazole derivatives having utility as herbicides.
There is a continuing need in agriculture for effective herbicides both for broad spectrum and selective use, and it is important to be able to synthesize these needed herbicides.
2. Description of the Prior Art
In the prior art U.S. Pat. No. 3,435,047 (Mar. 25, 1969), teaches a process for preparing 3-aminoisoxazole derivatives. The therein disclosed method involves reacting propiolonitriles with hydroxylamine in the presence of an alkali metal hydroxide.
Also in the prior art is Wahlberg, Ber. 65B, 1857-64 (1932), C. A. 27, 957.sup.3 (1933), wherein is disclosed the preparation of 3-tert-butyl-5-imino-4,5-dihydroisoxazole from pivalyl acetonitrile in acetic acid as the solvent, in reaction with the calculated amount of hydroxylamine hydrochloride and sodium acetate.
Another prior art reference is Japanese Pat. No. 11616/65 (Derwent Basic No. 17,246), which is directed to a process for converting 3-carbamoyl-5-alkyl isoxazole to 3-amino-5-alkyl isoxazole by the Hoffmann reaction.
Yet another prior art reference is U.S. Pat. No. 4,062,861 (Dec. 13, 1977), the U.S. counterpart of Belgian Pat. No. 818,161 (Derwent No. 00128W/01), which is directed to herbicidal isoxazolylurea derivatives. Among the starting materials utilized in preparing the compounds disclosed and claimed in this reference is 3-amino-5-(t-butyl)isoxazole. However, there is no teaching in this reference of the method of preparing this starting material.